Solvent-free adhesive ionic elastomer for multifunctional stretchable electronics

Intrinsically stretchable and transparent ionic conductors are of great interest due to their promising applications in flexible and wearable electronics. However, hydrogels/organogels based devices suffer from instability due to liquid evaporation or leakage. Herein, we present a solvent-free ionic elastomer (IE), featuring high transparency (>92%), stretchability (300%), ionic conductivity (0.07 mS/cm), adhesiveness (61 N/m), thermal stability (300 °C), and negligible mechanical hysteresis, which endows implementation capacity in multifunctional stretchable electronics. The IE-based robust strain sensors (both resistive and capacitive) show linear sensitivities in the range of 0–150% strain and long-term stability. Moreover, a reversible wide-range temperature sensor is presented showing remarkable sensitivity in the range of 30–55 °C sustained under 50% stretching. The temperature-strain effect on the IE-based sensor is insignificant, ensuring an accurate sensing capability. Thanks to its self-adhesiveness, a fully integrated, stretchable motion energy harvester as well as a skin-like thin triboelectric sensor array using IE as the electrode are further designed to demonstrate efficient human motion energy harvesting with a peak power density of 3.6 W/m² and self-powered tactile sensing. The results provide strategies towards potential applications of developed IE in healthcare monitoring systems, biomechanical energy harvesting, soft robotics, and human-machine interfaces.